Characterization of a Culture System for Rat Retinal Ganglion Cells: Towards a Screen for Potential Neuroprotective Compounds
DiPonio, Sarah M.
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The main excitatory neurotransmitter in the central nervous system (CNS) is the amino acid L-glutamine (L-glu). Over-activation of specific subtypes of glutamate receptors (i.e. N-methyl D-aspartate (NMDA) and kainate (KA)) can cause cell death in both primary and purified cultures of retinal ganglion cells (RGCs) from adult and postnatal mammalian retinas. The purpose of this study was to develop a method, which would yield an in vitro primary culture of viable retinal cells, and further to generate a methodology for a culture of purified retinal ganglion cells. These cultures were then used as a way to confirm the neuroprotective effects of specific glutamate antagonists such as the MNDA specific antagonist, MK-801. The cultures were also used to examine the possible neuroprotective effects of activating acetylcholine receptors, specifically the nicotinic variety. Excitotoxicity assays were performed on the primary cell cultures and the ''panned'' cultures containing RGCs and excitotoxicity was determined by measuring lactate dehydrogenase (LDH) levels. Primary cell cultures containing the assortment of retinal cells were routinely obtained, whereas the ''panned'' cultures often yielded RGCs in low numbers, as has been reported. LDH levels of primary cultures treated with glutamate increased rapidly over a 20-day period in comparison to controls. In the presence of the NMDA specific antagonist MK-801, as well as nicotine and the nicotinic agonist AR-R 17779, cells released less LDH than control cells. MK-801, while valuable as a research tool, has little value as a potential therapeutic drug due to its side effects (comparable to LSD). On the other hand, nicotine and AR-R 17779 have the potential to be used as therapeutic drugs in the treatment of glaucoma and other neurodegenerative diseases in the CNS.